1. Field of the Invention
The present invention relates to eyeglasses, and in particular relates to safety glasses lens mechanisms and safety glasses.
2. Description of Prior Art
Personal eye-protection, also referred to herein as safety eyewear and safety eyeglasses, are used to protect a user's eye during an activity which may pose risks to the eyes. Safety eyewear may need to satisfy standards in order to be considered safe (e.g, American standard ASTM F803-1 and European standard EN166). Eyewear satisfying these safety standards may be constructed to offer extra lens retention strength to prevent the lens (which may be a thicker lens type to prevent breakage) from falling out of the frame during high speed particle impact. To achieve this extra lens retention strength, the lens groove may need to be much deeper (for example, a minimum 1 mm) than normal eyeglasses, which may normally only have a groove depth of 0.5 mm. The deeper lens groove, especially in a more rigidly built injection frame style, may make it difficult to insert lenses.
U.S. Pat. No. 7,137,700 to DiChiara, et al. (DiChiara) discusses eyewear frame assembly including impact resistant eyewear frame assembly having a split frame and a fastener reinforcement. The frame has an aperture for receiving a lens and is split to expand upper and lower portions of the frame to insert or remove the lens from the aperture. First and second projections extend outwardly from the upper and lower frame portions, respectively.
U.S. Pat. No. 6,227,665 to Pernicka, et al. (Pernicka) discusses sport eyeglasses having removable lenses formed of a one piece plastic molded frame that includes a pair of lens receiving sections, a pair of opposite strap receiving temple sections and a central bridge section integral with the lens receiving sections are described herein. The bridge section is split to define an upper bridge part and a lower bridge part that are capable of being manually distanced from one another so as to define a gap and allowing lenses to be mounted in the lens receiving sections.
U.S. Pat. No. 7,553,014 to Yang et al. (Yang) discusses a spectacle frame including a spectacle frame front. The spectacle frame front includes a pair of spaced apart and opposed arms. The outer end of at least one arm of the pair of arms includes a lens retainer integral therewith for gripping and retaining a lens between the pair of spaced apart and opposed arms.
Frames may have split ends at the sides (see for example, DiChiara) or in the center (see for example, Pernicka) to allow expansion of the aperture to receive a lens or lenses. However, the split ends may make molding and production difficult, and may not be totally reliable in terms of lens retention as the screws connecting the split ends may tend to loosen over time. This loosening may create a dangerous condition in that the lenses of the safety eyewear may not be secure, but this condition may not be visible upon a visual inspection of the safety eyewear. Additionally, separable temple pieces may reduce the strength of a lens holding system.